1. Field of the Invention
The present invention relates to an LSI (large scale integrated circuit) design support system for a function design of LSI based on a graphic input method, and particularly to an LSI design support system which can realize rationalization of the design work.
2. Description of the Prior Art
Generally, as conventional function designs of LSI, there are a design of static circuit operation and another of a state transition system for determining the order of the circuit operation and controlling the operational states.
In such types of designs, designers described directly with a special language. Therefore, the designers must be limited to those who are well versed in the special language.
To solve the problem, there is a design support system of LSI based on a graphic input system, which can perform the function design of LSI without any special language for description even when the designer does not have special knowledge of the language. When the graphic input system is used for designing all the circuit operation, each circuit for expressing a predetermined function thereof can be graphically shown to complete the function design. However, the conventional graphic input system is always employed for the design of a circuit in an operational state. In such a design input system, circuit operation states always input the operational states. Therefore, the states of circuit operation are expressed by providing flip-flops for respectively assigning the operational expressions in the circuit. Each flip-flop is given a state signal which serves as a control signal for expressing the corresponding circuit operation. Accordingly, in this case, a great many of flip-flops must be required, and a circuit diagram to be obtained must be in a large scale and complicated.
While, in the design of a state transition system, there is a method of expressing order of a state translation by assignment of transitional conditions C1 to C6 between respective states st0 to st4 as shown in FIG. 1A. In a transition system shown in FIG. 1B, when 1 is inputted to a state q0, the state q0 changes into a state q1 and 1 is outputted therefrom. The fact is also expressed by a state transition table as shown in FIG. 1C. Conventionally, there is also a known design support system based on a graphic input method by using a table for expressing a transition system as stated above.
However, when the number of the transition states is large, the transitional conditions to be nested in the state transition table are increased so that a state transition diagram to be obtained becomes extremely complicated and difficult to understand. Moreover, when the transition conditions are complicatedly nested in the table, it becomes difficult for the designer to guess the relationship between the transition states so that a lot of time must be required for the design work. Thus, it is difficult to smoothly carry out the design work by such conventional methods.
Moreover, in a conventional design of circuit operation and a transition state system, a state transition diagram or a state transition table is designed separately from the circuit operational portion. Thus, there is not a known method of designing circuit operation and a state transition system at the same time using a circuit diagram, a state transition diagram and a state transition table together. Therefore, it is difficult to efficiently carry out a design with grasping both the circuit conditions and the circuit operation. Namely, in the conventional LSI design support systems, the circuit operation and the state transition system are designed separately by the graphic (circuit diagram) input, thus it takes much time to carry out designs based on such systems.
Furthermore, when the conditions of the state transition are not decided, the design must be stopped at the stage. Therefore, to carry out the design efficiently, the transition conditions should be completely defined in advance, however, once defined, the conditions cannot be added or changed on the way of the circuit design. Accordingly, it is difficult to carry out a flexible design therefor.